1. Field of Invention
The present invention relates to engine crankcase ventilation systems adapted to control by-pass gases composed of blow-by gas and fresh air. More particularly, the invention relates to an improved scavenging mechanism for separation of oil from a flow stream of by-pass gases entrained with oil and unburned fuel and water vapors, and to result in improved ventilation flow control.
2. Description of the Prior Art
Those skilled in the art will appreciate, contrary to ideal expectations, that combustion gases are not normally confined to the combustion chamber and exhaust manifold areas of an engine. A phenomenon called xe2x80x9cengine blow-byxe2x80x9d unfortunately assures that some of the combustion gases will escape the combustion chamber and flow into the engine crankcase, irrespective of the quality of the engine and/or the piston rings employed. Engine blow-by occurs on the power stroke of an internal combustion engine; i.e., the normally downward stroke of the piston caused by ignition of the fuel air mixture during the combustion cycle.
The typical mechanism for relieving an otherwise substantial crankcase pressure buildup has been the so-called PCV (positive crankcase ventilation) valve. The standard PCV valve, however, has been deficient in several respects. For example, the valve has not consistently provided satisfactory by-pass gas flows under the full range of engine performance, i.e., from idle through full wide-open throttle conditions, and particularly as impacted by wear due to operation. For example, under very high rpm conditions, the valve has often been ineffective to fully relieve crankcase pressure, particularly under high engine loads or low vacuum conditions. In addition, the typical PCV valve system has been ineffective to separate entrained oil from the flow stream of unburned gasoline and water vapors, even where orifices and deflectors have been employed.
Although several efforts have been made to improve overall performances of scavenging mechanisms designed to remove entrained oil from flow streams of blow-by gases, including unburned gasoline fuel and water vapors, such efforts have been met with only limited success, and been relatively expensive. In some cases, complex apparatus installed on the engine for such purposes has contributed only a small benefit for a significant inconvenience.
Finally, such apparatus has not only been relatively complex, but also difficult to maintain. Indeed, in some cases the complexity has outweighed any advantages because of extensive maintenance required for proper continuous system operation.
The present invention provides an improved engine crankcase bypass system that incorporates a scavenging mechanism adapted for collection and removal of oil entrained in engine bypass gases. Such gases normally include unburned gasoline fuel and water vapors. The improved ventilation system, designed to replace a standard PCV (positive crankcase ventilation) system, senses manifold and crankcase vacuum pressure, and via either an electronic or mechanical valve makes continuous adjustments of bypass gas flows to maintain a constant gas flow in excess of normal engine bypass gas flow rates. A deflector system installed conveniently within, an engine rocker cover is positioned in the bypass flow stream, and is designed to extract and separate oil vapor from the unburned gasoline fuel and water vapors entrained in the bypass gases. The oil is collected and returned to a reservoir for subsequent re-entry into the oil sump of the engine. The fuel and water vapors are allowed to continue to the intake manifold of the engine for reburning of the fuel.
In the described embodiment, the scavenging mechanism is effective to remove a high percentage of oil otherwise lost through the exhaust system per approximately 400 miles of driving. A transient oil reservoir is designed to have sufficient capacity to accommodate the oil extracted from the bypass gases. Upon shutting off the engine, vacuum produced by the engine is terminated, and oil collected in a transient reservoir is drained into an engine oil sump. The later action is facilitated by the release of a normally closed drain valve.